ElongationsfaktorenSystem

Elongation factors are conserved GTP-binding proteins that catalyze the elongation phase of protein synthesis on ribosomes. They coordinate the delivery of aminoacyl-tRNA to the A site and the translocation of tRNA and mRNA after each peptide bond is formed. By cycling between GTP-bound and GDP-bound states, these factors ensure accurate decoding and stepwise progression of the ribosome along the message. They are essential components of the translational machinery in all domains of life and interact with ribosomal subunits, tRNAs, and other translation factors to regulate speed and accuracy.

In bacteria, the core factors include EF-Tu, EF-Ts, and EF-G. EF-Tu binds aminoacyl-tRNA in a GTP-dependent manner, forming a ternary complex that delivers the tRNA to the A site. Correct codon-anticodon pairing triggers GTP hydrolysis and release of EF-Tu. EF-Ts acts as a nucleotide exchange factor that recycles EF-Tu back to the active GTP-bound form. EF-G binds the ribosome after peptide bond formation and, through another round of GTP hydrolysis, drives translocation, shifting the ribosome to the next codon.

In eukaryotes, the counterparts are eEF1A and eEF1B for aminoacyl-tRNA delivery and exchange, and eEF2 for translocation. eEF1A substantially mirrors EF-Tu in function, while eEF2 performs the translocation step. Eukaryotic elongation factors are integrated into broader regulatory networks and can be targeted by toxins, such as diphtheria toxin, which inhibits eEF2 by ADP-ribosylation to block translocation.

Elongation factors are essential for growth and are among the most conserved components of the translation apparatus. Their proper function ensures efficient and accurate protein synthesis, making them relevant in basic biology, clinical contexts, and research into antimicrobial strategies.